1. Field of the Invention
Embodiments disclosed herein relate generally to polymer coated particulate materials. In another aspect, embodiments described herein relate to a process to produce polymer coated particulate materials. In more specific aspects, embodiments described herein relate to particulate materials such as polymer coated sands. The sands or other particulate materials may be coated or incorporated with a polymer or polymeric mixture, where the polymer or mixture of polymers may be supplied as an aqueous dispersion.
2. Background
Artificial turf consists of a multitude of artificial grass tufts extending upward from a sheet substrate. Infill material dispersed between the artificial grass tufts maintains the artificial grass tufts in an upright condition, preventing them from lying down flat or in another undesirable manner.
As one example of materials used as infill, U.S. Patent Application Publication No. 20060100342 describes infill formed by coating silica sand with either elastomeric materials or thermoplastic polymers. The infill granules are formed by first heating a portion of the silica to a temperature between 200° C. and 300° C., placing the sand in a mixer, and adding elastomer or thermoplastic polymer pellets while mixing. The thermoplastic polymer then melts, coating the sand. The contents of the mixture are then cooled using a water spray and air flowing through the mixer. The exact amount and timing of the water spray is critical to result in a free-flowing material without significant formation of agglomerates.
As another example of materials used as infill, U.S. Patent Application Publication No. 20050003193 describes infill granules formed by coating a core of recycled tire material with a plastic. The infill granules are formed by mixing the plastic and the recycled tire granules, melting the plastic, and rolling the mixture to form sheets. The sheets are cooled, solidifying the plastic, and then the sheets undergo granulation, resulting in the plastic coated recycled tire granules for use as infill.
The choice of infill material, core and coating, may greatly influence the overall characteristics of the artificial turf. Desired properties of infill include: homogeneous and complete coating of the particulate substrate, resulting in both good appearance and good wear resistance; good skid and heat resistance for long term use, avoiding compaction of the infill; soft coatings providing the desired haptics, aesthetics, and player safety; and, the infill needs to be free flowing for ease of application.
Infill materials produced as described in the patents and publication referenced above often result in infill that does not exhibit a good balance of the desired properties. In addition, the processes used may be inefficient, result in an incomplete coating of the granular material, or produce excess agglomerates.
Accordingly, there exists a need for improvements in the processes used to produce infill. It is desired to have a process that provides a lower cost with reduced waste. It is also desired to have a resin that provides a uniform, homogeneous coating, resulting in superior wear resistance, good haptics and aesthetics, and excellent player safety. Improvements are also needed in the resulting properties and the overall balance of the properties of the infill.